Federal Aviation

MMEL Policy Letter PL -38, Revision 1                          


August 15, 1997 


All Region Flight Standards Division Managers
All Aircraft Evaluation Group Managers


Manager, Air Transportation Division, AFS-200

Reply to Attn of:

Manager, Technical Programs Branch, AFS-260


Policy Regarding MMEL Relief for Primary Thrust Setting Instruments on Two-Engine Airplanes




PL-38, Original, dated September 15, 1989

Information previously published in PL-2, dated July 21, 1976


This policy letter provides the FAA policy regarding dispatch of a two-engine airplane with a primary thrust setting instrument (EPR or N1) inoperative.



Revision 1 contains reformatting, but the policy is unchanged.

This Policy Letter provides policy for inoperative primary thrust setting instruments.  Previous FAA policy (PL-2, Dated July 21, 1976) disallowed primary thrust setting instrument (i.e., EPR gage) inoperative on two engine airplanes.  This was because MMEL relief is based on the premise of additional failures occurring enroute, and no relief could be granted for such instruments since a subsequent failure of the engine with the operative thrust setting gage would leave the flight crew with no reference for setting thrust.


The FAA has since modified their position and now permit such dispatch relief provided that another engine instrument is certified to be a primary means of setting thrust. Such a certification must comply with all rules dictated by FAR Part 25.



FAR 25.1305 (d)(1) imposes a requirement for turbojet aircraft to be equipped with, an indicator to indicate thrust, or a parameter that is directly related to thrust, to the pilot. Dispatch relief for an instrument which is certified as the means of complying with this FAR may only be granted if another instrument on the affected engine is also certified as a means of complying with this FAR.


Actual MMEL limitations and specific wording should be developed by the assigned FOEB Chairman after coordination with appropriate parties.  Since this type of MMEL relief is contingent upon development and approval of data under FAR Part 25 rules, the appropriate FAA Aircraft Certification Office should be included in this coordination.

Each Flight Operations Evaluation Board (FOEB) Chairman should apply this Policy to affected MMELs through the normal FOEB process.






Air Transportation Division, AFS-200




PL-38, R  1 reformatted 02/04/2010 with no change to content.